(i) Technical Field
The present invention relates to a toner for developing an electrostatic image that is used upon developing an electrostatic latent image, which is formed by an electrophotographic process, an electrostatic recording process or the like, with a developer, a method for producing the toner, a resin particle dispersion liquid that can be used as a raw material of the toner, and a method for producing the resin particle dispersion liquid. The invention also relates to a developer for developing an electrostatic image and a method for forming an image using the toner for developing an electrostatic image.
(ii) Related Art
As an ordinary polycondensing method for obtaining a polyester resin for a toner for developing an electrostatic image, particularly an amorphous polyester (which is also referred to as non-crystalline polyester in some cases), such a method has been employed that requires large energy, i.e., agitation with large motive energy at a high temperature exceeding 200° C. due to the low reactivity of the monomer, and a reaction time far more than 10 hours under highly reduced pressure.
Upon producing a polyester resin having low reactivity, a metallic catalyst having high activity in a high temperature range has been generally used.
However, the technique using a Bronsted acid containing sulfur atoms as a polycondensation catalyst of polyester is capable of attaining low temperature polymerization at 150° C. or lower, and is significantly important for the global environmental protection from the standpoint of reduction in total production energy of a toner.
A method for producing a polyester resin aqueous dispersion liquid includes such related-art methods as a solution method, a phase inversion emulsification method and a high temperature emulsification method. The solution method requires large investment in recovery equipments and is not favorable from the standpoint of environmental safety, and it also has a problem in image quality, such as fogging in a non-image area caused by a remaining solvent of the toner, since the solvent cannot be completely removed.
For producing self-emulsifying polyester, a hydrophilic polymer having a particular structure of a salt thereof (sulfonylphthalic acid, such as sulfonic acid or an alkaline neutralized salt thereof, such as PDPS) has been used, but it has a problem in practical use due to reduction in volume resistivity and deterioration of charging property in a high temperature and high humidity environment, upon using as a resin for a toner.